Boiler adjusting max useful heat output

[GoodDIYjob]

Indeed. Get a couple of grand set aside. The Biasi is crap, but they could chug along fine for a good while. You just don't want to get caught short and not in a position to pick a good replacement option (including the installer) over a convenient one (easy but expensive finance).

As for your original question, I'd be more inclined to think you have a sluggish pump, which, for the age of the boiler, is not a surprise.

Yes, thanks. I'll start saving. You could well be right for the pump. Unless I have the flow temp above 70C the two largest rads in the system, downstairs dining and lounge, don't heat up more than half height.

I've taken all the rads out side and hosed out. They weren't too bad. and there is a mag filter on for the last 2 years.

Is there any other way to diagnose the lazy pump?

Thanks again

 

[Dan Robinson]

Various discussions on this already on the forum (not necessarily specific to your boiler).

Might be worth a final repair though if the boiler is otherwise reliable.

 

[GoodDIYjob]

Various discussions on this already on the forum (not necessarily specific to your boiler).

Might be worth a final repair though if the boiler is otherwise reliable.

Ok, I've done everthing I can do to flush system, put cleaner in for a week, taken rads outside to hose out, balanced carefully, new valves (TRVs upstairs) most upstairs rads are only 1/4 turn on. The boiler is upstairs, relocated to the original airing cupboard where the HW tank would of been.

I'll have a search for diagnonsing slow pump, yes I know what you are saying, I was thinking the same just hoping to avoid for a bit longer. Having children is expensive!

 

[Dan Robinson]

Once diagnosed, a new pump could buy you plenty of time. Any functioning boiler, from a user point of view, is a good boiler.

 

[bernardgreen]

from your vaaaaaaasssst range of experience in these matters,

Second hand knowledge collated from the knowledge of a man who designed boilers, large ones for commercial and industrial applications.

 

[Dan Robinson]

So, like much of your information, useless and irrelevant.

 

[bernardgreen]

So, like much of your information, useless and irrelevant.

That is your opinion and you are welcome to have that opinion.

I would consider the knowledge of a person whose career was designing boilers to be as good, if not better, than the knowledge of a person who installs and repairs boilers.

 

[Dan Robinson]

Pahahahahahahahahahahahahahwhwhwhahajajajaanhah

 

[dilalio]

I would consider the knowledge of a person whose career was designing boilers to be as good, if not better, than the knowledge of a person who installs and repairs boilers.

BG there is a huge difference between “collating” knowledge from someone else and “gaining” knowledge, through years of experience, for yourself. Perhaps you should “consider” that, before spewing forth!

 

[EAST61]

Pahahahahahahahahahahahahahwhwhwhahajajajaanhah

I saw a “Jennings heating & plumbing ltd” van around Slough the other day and thought it might be you. Looks like someone has set up a new company with a very similar name.

 

[Dan Robinson]

That is your opinion and you are welcome to have that opinion.

I would consider the knowledge of a person whose career was designing boilers to be as good, if not better, than the knowledge of a person who installs and repairs boilers.

So how many domestic boilers have YOU designed and serviced over the last 20 years? You J&S schitbox?

I notice you have not answered my question about which specific boilers you would or would not recommend. Otherwise it is a pretty useless bit of advice.

What relevance does a commercial boiler designer have to the domestic market, and how many has this imaginary friend come across?

I saw a “Jennings heating & plumbing ltd” van around Slough the other day and thought it might be you. Looks like someone has set up a new company with a very similar name.

None of my vans are sign written. Although I do have embroidered seat covers in mine. Don't routinely cover Slough either. It is a common enough name though. There is a big outfit in the States with the same name too,

 

[bernardgreen]

So how many domestic boilers have YOU designed and serviced over the last 20 years?

How many have you designed ? Servicing may not provide much knowledge about the design features and the reason for those features being part of the design.
That said I do respect your experience and ability in installation and servicing.

I notice you have not answered my question about which specific boilers you would or would not recommend. Otherwise it is a pretty useless bit of advice.

In the context of a boiler being cycled the information that some boilers are more resilient to cycling than others has some relevance. Your experience might provide some answers as to which are the most tolerant.

What relevance does a commercial boiler designer have to the domestic market,

He probably has a very good knowledge of the combustion process and the various forms of heat exchanger that can be used in commercial and domestic boilers.


Unlike you

You J&S schitbox?

I do not, on a public forum give adverse comment about an item without providing a reason that is already in the public domain. Is there a public domain source that supports your opinion of J&S boilers that you can post here.

 

[Dan Robinson]

I do not, on a public forum give adverse comment about an item without providing a reason that is already in the public domain.

Experience.

Also, remember Bernie, you're talking about second hand knowledge, of a person not even working in the same field.

Chinese whispers springs to mind.

 

[D_Hailsham]

Yes, I've found out it can be adjusted from the manuals but surely it can't be adjusted the min output of the modulation of the gas valve?

That's correct. However many boilers automatically restart at max output and then modulate down. Setting the max to, say, 15kW would reduce the "overload" on the rads and may extend the "on" periods.

The 12.7KW in the manual as minimum useful output is at a calorific value of 34.02MJ/M3 which according to the bills I receive, is quite a lot lower than the MJ content of UK natural gas which is 39.4 on my bill?

I suspect that Biasi is quoting Net Calorific Value, and your supplier Gross Calorific Value.

I used the baxi heat loss calc link you gave, it says 14.9kw. But that must be over rated?

I am surprised as the methodology, U-values etc, is based on work done by the Building Industry Research Association.

As the result is about twice what you anticipated, did you enter the height correctly? It asks for the height of a floor (which is multiplied by the number of floors), not the total height from ground floor to top ceiling.

You say that you have 8-9kW of rads. How did you arrive at this value?

 

[GoodDIYjob]

That's correct. However many boilers automatically restart at max output and then modulate down. Setting the max to, say, 15kW would reduce the "overload" on the rads and may extend the "on" periods.


I am surprised as the methodology, U-values etc, is based on work done by the Building Industry Research Association.

As the result is about twice what you anticipated, did you enter the height correctly? It asks for the height of a floor (which is multiplied by the number of floors), not the total height from ground floor to top ceiling.

You say that you have 8-9kW of rads. How did you arrive at this value?

Thanks for replies.

1. Yes, ok I did wonder how the modulation would work as it seems to be modulating down to around the min gas rate but I did gas rate when it was 60C plus flow temp so does the modulation control come in at higher flow temps. I suppose not range limiting helps with initial heat up.

2. Ok, yes I could try and do a bottom up calc from U values myself out of the SAP manual guidance on main construction elements. Takes a while though...and with a 1930s property, the estimates are pretty generic sometimes.

Ceiling height I put in 2.5M x 2 floors. Approx 10mx6m foot print. Semi. Cavity walls, no insulation in walls or suspended floor. I just did it again and this time 12.5kwh so a bit lower. It still feels a little high to me..

3. Rads outputs

Recently replaced Myson Premier - single panel

1. 1800 x 600 specs at delta 50C, 1.7kw
2. 1100 x 600 specs at delta 50C 1kw


Old (assumed) myson imperial single panel rads

3. 1290 x 600 - specs from myson single (1200x600) 1.1kw
4. 965 x 600 - specs from myson single (900x600) 0.8kw
5. 965 x 500 - specs from myson single (900x600) 0.8kw

6. Replaced Lounge single panel (unkown brand) 1800 x 600 use per myson premier 1.7kw
7. Towel rail 600 x 1000 guesstimate 0.4Kw
8. Conservatory double panel on frost setting, 1000x600 guesstuimate 1kw

Total excl conservatory 7.5kw
Total incl conservatory 8.5kw

On Sat it was -1C outside and took about 2 hours to climb 2.5C. Since it has warmed up a little since then the response is much faster, this morning I think the thermostat was off at 18.5C after about 1 hour in the morning...

So my logic is the heatloss can't be more than 7 or 8kw given that is the useable heat available inside from the rads.(plus internal gains but fairly insignificant?)...and it still heat.

Thanks again for your interest.